The Israeli military is carrying out its deepest incursion into Lebanon since its withdrawal from the country a quarter-century ago, despite a nominal ceasefire agreement brokered by the United States and the first direct talks between the two countries in decades.

Israel’s offensive poses a challenge to the impending extension of the ceasefire in the Iran war, as Tehran also hopes to reach any agreement that would end the war in Lebanon.

On Sunday, Israeli forces captured a symbolic fort in southern Lebanon that overlooks all of Lebanon and northern Israel. The last time they seized it, they held it for 18 years.

The fort is named Beaufort, also called AI-Shaqif. It was built around the 12th century as a Crusader castle and was later used by Saladin’s army in Jerusalem, the Mamluks, the Ottomans, the French Mandate, and the Palestine Liberation Organization.